Adjusting cooling air in glass tempering machine

ABSTRACT

A method and an equipment for adjusting the cooling air of a glass tempering machine. Cooling air is led by at least one fan ( 1, 2 ) to a tempering area ( 4 ) for cooling the glass exiting a tempering furnace ( 11 ). By means of a closing device ( 10 ) the tempering area ( 4 ) can be reduced such that a tempering zone with a pressure that can be raised sufficiently high for tempering thin glass can be formed out of the reduced tempering area. In this manner the tempering result becomes very even, and no separate tempering zone is needed even for thin glass.

The invention relates to a method of adjusting the cooling air of aglass tempering machine, in which method cooling air is led to atempering area for cooling the glass exiting a tempering furnace.

The invention also relates to an equipment for adjusting the cooling airof a glass tempering machine, the equipment comprising at least one fanand a channel system for leading cooling air to a tempering area forcooling the glass exiting a tempering furnace.

When tempering glass, the temperature of the glass is increased abovethe softening point of glass in the tempering process. For this purposetempering furnaces are used, currently typically what are known asoscillating roller furnaces. After the tempering furnace the glass isled to temper cooling. Tempering thin glasses, typically with athickness of 2.8 to 3.8 mm, requires a high tempering pressure providedby a fan, e.g. a pressure of about 20 to 25 kPa. The alternative is touse the combined effect of fan air and compressor air, whereby an about8 to 10 kPa tempering pressure is sufficient with the tempering effectpractically emanating from the compressor. Thin glasses are temperedeither in a separate tempering zone through which the glasses areconveyed without stops. After the tempering zone, the glasses are led toan after cooling unit where they are oscillated in a reciprocatingmanner upon rollers. The blast pressure of the tempering zone isprovided e.g. by series connected high-pressure fans. Such a separatetempering zone involves expensive equipment and structural investments.Furthermore, said tempering zone cannot be utilized in connection withglasses with a thickness of 4 mm or more, the after cooling unitoperating as their tempering unit. Tempering thin glasses may beimplemented also without a separate tempering zone by blowingpressurized air at the glasses both by fans and by the compressor. This,however makes the anisotropy pattern of the glass quite uneven as theair jets are formed spotlike. Furthermore, a separate compressor isneeded, and, in order to increase the capacity, the compressor should beexpanded with increased capacity.

On the other hand, when tempering thick glasses, the blast pressure hasto be sufficiently low. Typically this problem is solved by adjustingthe speed of rotation of the fan motors. Fl 77,216 discloses analternative way to achieve low blast pressure. Said publicationdescribes a solution with at least two fans, fan channels between thefans and the air delivery chamber, and a bypass channel connecting thefan channels. A gate valve is disposed after the bypass channel 7between the fan channel and the air delivery chamber, the plate being inthrottle position when one fan is switched on with the guide vanecontrol closed and another fan is switched off with the guide vanecontrol partially or entirely open. The air is led by the bypass channel7 to the channel of the other fan, from where it exits via the openguide vane control. This way, the gate valve being in its maximumthrottle position, the desired minimum pressure is achieved for thenozzles. Said solution and adjusting the speed of rotation of the fanmotors require, however, a completely separate solution in temperingthin glasses.

It is the object of the present invention to provide a method and anequipment for avoiding the above mentioned drawbacks and forimplementing temper cooling simply within a wide range of glassthickness.

The method of the invention is characterized in that the tempering areais reduced by closing a closing device that can be opened and closed,whereby a tempering zone with a pressure that can be raised sufficientlyhigh for tempering thin glass can be formed out of the reduced temperingarea.

The blast pressure unit of the invention is characterized in that itcomprises a closing device for directing blast air at only a part of thetempering area, whereby a tempering zone with a pressure that can beraised sufficiently high for tempering thin glass can be formed out ofthe reduced tempering area.

It is an essential idea of the invention that the tempering area can bereduced by a closing device, whereby a tempering zone with a pressurethat can be raised sufficiently high for tempering thin glass can beformed out of the reduced tempering area. Furthermore, the closingdevice can be opened for the after cooling of thin glasses or thetempering of thicker glasses, for example. It is the idea of stillanother preferred embodiment that the tempering area is reduced to atempering zone of half the size of the tempering area. It is the idea ofanother preferred embodiment that the equipment comprises at least twofans which can be connected both in series and in parallel by means ofchannel systems and a gate valve.

It is an advantage of the invention that the tempering result achievedis very even. Furthermore, space is saved as no separate tempering zoneis needed even for thin glasses. This also lowers acquisition costs. Aseparate compressor is not needed either, but instead two moderatelysized fans are sufficient to provide tempering air to the entirethickness area of the glass.

The invention will be described in more detail in the attached drawingsin which

FIG. 1 schematically shows an equipment according to the inventionadapted for thin glasses,

FIG. 2 shows the equipment of FIG. 1 adapted for medium-thin glasses,

FIG. 3 shows the equipment of FIG. 1 adapted for medium-thick glasses,and

FIG. 4 shows the equipment of FIG. 1 adapted for thick glasses.

FIG. 1 schematically shows a blast pressure unit according to theinvention. The blast pressure unit comprises a first fan 1 and a secondfan 2, connected by a channel system 3 for blast air at the temperingarea 4. A by-pass channel 3 a is further connected to the channel system3, but is closed in the case of FIG. 1 by a first gate valve 5 of thebypass channel 3 a and by a second gate valve 6 of the bypass channel 3a such that no air flows in the bypass channel 3 a. Instead, the airoriginating from the first fan 1 is led to the second fan 2, from whichthe air is led further, i.e. the first fan 1 and the second fan 2 arecoupled in series. A suction port 7 in the second fan 2 is closed by agate valve 8 in the suction port 7. The travel of air to temperingnozzles disposed above and below the glass is controlled by a regulatingdevice 9 which uses throttle control to adjust the desired temperingpressure on the upper and lower sides. A closing device 10 is in itsclosed position, the tempering blast being led only to the end of thetempering area 4 facing the tempering furnace 11, i.e. the first part 4a of the tempering area 4. The latter part 4 b of the tempering area 4becomes thus depressurized and a maximum tempering pressure of about 20to 25 kPa, for example, is reached in the first part 4 a. In FIG. 1, theairflow is illustrated by arrows.

After the tempering furnace, thin glasses, in this context glasses witha thickness of 2.8 to 3.8 mm, are led through the first part 4 a of thetempering area 4 operating as the tempering zone, the blast pressureunit being adapted in accordance with FIG. 1. The area of the temperingzone is preferably about one half, i.e. 35 to 65%, of the area of thetempering area 4. When the glasses have passed across the pressurizedfirst part 4 a, the closing device 10 is opened, whereby the entiretempering area 4 is subjected to blowing. In addition, it is possible,particularly when full-length loads are concerned, to transport theglasses to an auxiliary conveyer disposed between a chiller and aloading table, from where they return to the blowing zone. Naturallythis blowing is significantly less pressurized than the blowing directedat the first part 4 a in the case shown in FIG. 1. The glass load isoscillated over the entire length of the tempering area 4, and it ispossible to aftercool thin glasses to processing temperature, althoughthen they are not subjected to so high a pressure as at the temperingstage.

FIG. 2 shows the equipment of FIG. 1 adapted for medium-thin glasses.The numbering of FIG. 2 corresponds to that of FIG. 1. In this context,medium-thin glasses refer to glasses with a thickness of 3.8 to 4.8 mm.The first gate valve 5 of the bypass channel 3 a has been turned suchthat the airflow of the first fan 1 is led to the bypass channel 3 a.Similarly, the gate valve 8 of the suction port 7 is opened such thatair is led from the suction port 7 to the second fan 2. Further, thesecond gate valve 6 of the bypass channel 3 a is adapted such that boththe airflow of the second fan 2 and the airflow of the first fan 1 viathe bypass channel 3 a can be led to the tempering area 4. The secondgate valve 6 of the bypass channel 3 a is in a centre position inequilibrium, whereby an equal amount of air at the same pressure can betaken from both fans. The gate valve 6 also operates as a pressurebalancer for the fans by adjusting the size of the inlet such that, whenneeded, it throtties one channel in case balance is lost. A temperingblast has been led to the entire tempering area 4 from the startingmoment, i.e. the closing device 10 is open all the time. Typically, theneed for tempering pressure is about 7 to 10 kPa. Thus the first fan 1and the second fan 2 operate connected in parallel, and the air blown bythem is fed to the entire tempering area 4.

FIG. 3 shows the blast pressure unit of the invention adapted formedium-thick glasses. The numbering of FIG. 3 corresponds to that ofFIGS. 1 and 2. In this context, medium-thick glasses refer to glasseswith a thickness of 4.8 to 10 mm. The second fan 2 is switched off andthe blast air of the first fan 1 is adapted to pass along the bypasschannel 3 a by means of the first gate valve 5 and the second gate valve6 of the bypass channel 3 a to the tempering area 4. The closing device10 is open, whereby the blast is directed at the entire tempering area4. The need for tempering pressure is in the range 3 to 5 kPa. Thepressure level is adjusted by the guide vane control of the fan. Thesecond fan 2 may also be used for blowing, whereby the first fan 1 isswitched off and the bypass channel 3 a is closed by the gate valves 5and 6 of the bypass channel 3 a. This way the fans can be used equally,whereby the bearings or other mechanics of either fan do not wearessentially more rapidly that that of the other, and the blast pressureunit remains in working order longer than if only one of the fans wereused.

FIG. 4 shows the blast pressure unit of the invention adapted fortempering thick glasses. The numbering of FIG. 4 corresponds to that ofFIGS. 1 to 3. In this context, thick glasses refer to glasses with athickness of 10 to 19 mm. Particularly when very thick glasses, i.e.thickness 15 to 19 mm, are concerned, the tempering pressure must bevery low, e.g. 50 to 100 Pa. In the case shown in FIG. 4, the second fan2 is switched off and only the first fan 1 is working with its guidevane control closed. The blast air of the first fan 1 is led to thebypass channel 3 a by the first gate valve 5 of the bypass channel 3 a.The second throttle 6 of the bypass channel 3 a is in an intermediateposition, whereby the air coming from the bypass channel 3 a is allowedto flow through the second fan 2 and further out of the suction port 7.The tempering pressure can be adjusted by means of the positions of thegate valves 6 and 8, and, when needed, also by means of the guide vanecontrol of the first fan 1. It is also possible for a part of the airproduced by the first fan 1 to be led out of the system directly via thegate valves 5 and 8, whereby the tempering pressure is adjusted by meansof the positions of these two gate valves.

In the blast pressure unit according to the invention, one of the fans,for example, may be a so-called two-speed fan, whereby a low temperingpressure is achieved by using the lower speed of rotation of the blastengine, and adjust the pressure level by means of the guide vane controlof said fan. Furthermore, the speed of rotation of the fan may beadjusted e.g. by means of inverter drive.

The drawing and the related description are only intended to illustratethe idea of the invention. As to its details, the invention may varywithin the scope of the claims. The glass thickness values presented inthe description serve only as examples, and, according to the need, eachpresented embodiment of the equipment may naturally be used with anotherglass thickness than that presented, depending on the fan dimensioning,for example.

What is claimed is:
 1. A method of adjusting the cooling air of a glasstempering machine, in which method cooling air is led to a temperingarea for cooling the glass exiting a tempering furnace, whereintempering area is reduced by closing a closing device that can be openedand closed, whereby a tempering zone with a pressure that can be raisedsufficiently high for tempering thin glass can be formed out of thereduced tempering area and that the glass is led through the temperingzone, after which the closing device, is opened and the glass isoscillated within the entire tempering area, the tempering area servingas an aftercooling unit.
 2. A method as claimed in claim 1, wherein thearea of the tempering zone formed out of the tempering area is 35 to 65%of the area of the tempering area.
 3. A method as claimed in claim 1,wherein the cooling air is provided by at least two fans, connectedeither in series or in parallel, depending on the thickness of theglass.
 4. An equipment for adjusting the cooling air of a glasstempering machine, the equipment comprising at least one fan and achannel system for leading cooling air to a tempering area for coolingthe glass exiting a tempering furnace, wherein the equipment comprises aclosing device for directing blast air at only a part of the temperingarea, whereby a tempering zone with a pressure that can be raisedsufficiently high for tempering thin glass is formed out of the reducedtempering area, means for leading the glass through the tempering zone,controlling means for opening the closing device after the glass is ledthrough the tempering zone and means for oscillating the glass withinthe entire tempering area, the tempering area serving as an aftercoolingunit.
 5. An equipment as claimed in claim 4, wherein the closing deviceis adapted such that the area of the tempering zone is 35 to 65% of thearea of the tempering area.
 6. An equipment as claimed in claim 4,wherein the equipment comprises at least two fans, a bypass channel andgate valves such that the fans can be connected both in series and inparallel.
 7. A method as claimed in claim 2, wherein cooling air isprovided by at least two fans, connected either in series or inparallel, depending on the thickness of the glass.
 8. An equipment asclaimed in claim 5, wherein the equipment comprises at least two fans, abypass channel and gate valves such that the fans can be connected bothin series and in parallel.